Atrial fibrillation is a common occurrence in cardiac patients. It is generally caused by the lack of blood output from the atria and usually leads to blood clots in the atria. The blood clots may lodge in either the lungs or the brain resulting in serious health problems, strokes or possibly death to the patient.
Various types of oral drugs have been tried to treat atrial fibrillation. While some patients are helped by these drug therapies, the majority of patients are not successfully and safely treated and require a different type of treatment. One of the most significant shortcomings of these drugs is the side effects they may have on the patients. Specifically, in some patients administration of these drugs leads to a ventricular fibrillation which is almost always immediately fatal.
Traditional prior art provides a number of devices and methods to control atrial fibrillation. Generally, the prior art discloses defibrillation systems which employ electrical shock to control atrial fibrillation. For example, U.S. Pat. No. 4,572,191 and U.S. Pat. No. 3,952,750 teach a standby electrical shock device for atrial defibrillation. Similarly, recently issued patents in this art disclose electrical shock therapy systems for atrial defibrillation. For example, U.S. Pat. No. 5,282,837, U.S. Pat. No. 5,265,600 and U.S. Pat. No. 5,391,185 disclose various embodiments relating to implantable electrical atrial defibrillator.
The use of electrical shock in the treatment of atrial fibrillation poses some hitherto unresolved problems. Primarily, electrical atrial defibrillation requires shocks in the order of one to two joules of electrical energy. This shock magnitude is very painful to the patient and is undesirable. Another significant disadvantage of electrical shock therapy is the fact that atrial defibrillation shock may lead to ventricular fibrillation. This is because a moderate level shock during the repolarization of the ventricles will typically lead to fibrillation. In order to avoid this problem the prior art utilizes methods and apparatus to sense the R-wave in the right ventricle and carefully synchronizes the atrial shock to avoid impinging upon the ventricular T-wave which would represent the repolarization of the ventricle. The risk of fibrillating the heart with an atrial defibrillation shock can also be minimized by delivering shocks which are timed with ventricular activity. This method is generally disclosed in U.S. Pat. No. 5,207,219, U.S. Pat. No. 5,350,402 and U.S. Pat. No. 5,411,524.
In spite of the advances made by the prior art, atrial defibrillation shock therapy may cause ventricular fibrillation and therefore a therapy for an otherwise non-fatal condition might be fatal to the patient. One possible solution is to incorporate a ventricular defibrillator with an atrial defibrillator. However, the energy required for ventricular defibrillation is significantly higher than is required for atrial defibrillation. Therefore, the capacitors and batteries need to be large and the device would need to be the same size as a conventional implantable cardiac ventricular defibrillator.
An alternate therapy for atrial defibrillation comprises drug injection devices. Specifically, for example, U.S. Pat. No. 3,923,060 and U.S. Pat. No. 4,146,029 disclose various types of implantable drug pumps which discharge an amount of drugs at the onset of atrial fibrillation. Similarly, U.S. Pat. No. 4,552,561 and U.S. Pat. No. 4,969,873 disclose a drug pump mounted on the outside of a patient's body for drug injection and a specialized drug chamber for a pump, respectively. Further, U.S. Pat. No. 5,041,107 discloses the use of iontophoresis for drug delivery.
Publications highlighting some of the critical limitations of the prior art and the need for alternate solutions include an article by Bloem et al., Journal of Electrocardiology Vol. 26 Supp. 1994, p. 60. This article suggests the use of implantable drug for atrial defibrillation. Further, the use of drugs for ventricular defibrillation is generally disclosed in U.S. Pat. No. 5,220,917 by Cammilli, et al., and in a publication in New Trends and Arrhythmias Vol. 8, No, 4 of 1992 in an article by Cammilli, et al., entitled "Immediate Ventricular Defibrillation by Automatically Retroinfused Drug and Coronary Sinus During Experimental Acute Myocardial Infraction in Swine". Similarly, the use of drugs in ventricular defibrillation is also disclosed in "Implantable Pharmacological Defibrillator (AI PhD): Preliminary Investigation in Animals" by Cammilli et al., published in Pace February 1991, Vol. 14. Further, in U.S. Pat. No. 5,305,745 Zacouto teaches the use of implantable injector of thrombolytic agents to break clots.
While prior art methods and devices have performed adequately, there is an acute need for a reliable means to control and manage atrial fibrillation without the problems and limitations associated with external or implantable electrical shock therapy. Accordingly, as will be set forth below, the present invention overcomes these and related limitations of the prior art. Specifically, the present invention utilizes a system and device for atrial defibrillation through the implementation of, inter alia, a self cleaning single/multiple drug delivery system, a cardiac pace monitoring and control system, antitachycardia pacing system, and a therapeutic and cardiac activity history recording and maintenance system.